Year | Value | 2021 | 9.1065001822548 | 2020 | 8.8276962613214 | 2019 | 8.6718201989068 | 2018 | 8.8538993381167 | 2017 | 9.0442244402473 | 2016 | 9.245903896731 | 2015 | 9.501027672569 | 2014 | 9.7200523219902 | 2013 | 9.9737056504814 | 2012 | 10.262436996166 | 2011 | 10.591660436744 | 2010 | 10.973964315055 | 2009 | 11.329433539509 | 2008 | 11.763466243739 | 2007 | 12.123795599937 | 2006 | 12.506290999096 | 2005 | 12.941115752437 | 2004 | 13.323079237464 | 2003 | 13.65841391507 | 2002 | 13.993757097687 | 2001 | 14.274860763189 | 2000 | 14.494149637574 | 1999 | 14.915110151543 | 1998 | 15.583957012886 | 1997 | 15.369644162958 | 1996 | 15.562275659372 | 1995 | 15.614595316861 | 1994 | 16.54075472885 | 1993 | 16.12893547304 | 1992 | 16.450026156957 | 1991 | 16.338617890276 | 1990 | 16.23393988924 | 1989 | 16.267245546929 | 1988 | 17.284814963749 | 1987 | 16.858844642563 | 1986 | 17.193887027488 | 1985 | 17.53912792994 | 1984 | 17.791465416017 | 1983 | 17.869288052274 | 1982 | 17.138712249052 | 1981 | 17.35198881213 | 1980 | 17.600033337131 | 1979 | 17.844385852501 | 1978 | 18.177419275674 | 1977 | 18.408697419495 | 1976 | 18.750350017232 | 1975 | 19.318265992983 | 1974 | 19.628046771983 | 1973 | 19.774463474449 | 1972 | 20.391172759717 | 1971 | 20.436853317412 | 1970 | 20.863863766617 | 1969 | 21.232866066302 | 1968 | 21.417683509927 | 1967 | 21.792068753141 | 1966 | 22.002401990247 | 1965 | 21.944502512562 | 1964 | 22.059329999347 | 1963 | 22.418489592414 | 1962 | 22.619673840497 | 1961 | 22.984020938597 | 1960 | 23.241669936758 |
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